1. Field of the Invention
Bleaching cellulosic wood pulp with ozone.
2. Review of the Prior Art
There is a great amount of prior art describing bleaching with ozone.
A recent patent is U.S. Pat. No. 4,080,249 which describes a number of conditions for bleaching wood pulp with ozone. Another recent patent, Eckert U.S. Pat. No. 4,119,486, describes bleaching with ozone in the presence of a cationic surfactant.
Kamishima "Ozone Bleaching of Kraft Pulp With the Addition of Methanol as Cellulose Protector," Japan TAPPI 31 No. 10, pp. 699-706 describes using methanol, in amounts of 80 to 100% of the weight of the pulp, to improve the viscosity of ozone-treated pulp. The examples have liquid phases ranging from 100% methanol to approximately 27% by weight methanol in water, equivalent to around 24.75 to around 7.8 moles methanol per liter of the liquid phase.
A second article dealing with additives in ozone bleaching is Osawa and Schuerch "The Action of Gaseous Reagents on Cellulosic Materials 1. Ozonization and Reduction of Unbleached Kraft Pulp," TAPPI February 1963, Vol. 46, No. 2, pp. 79-84. The additives were nitromethane and methyl acetate.